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Published: 2024-01-01 20:33:58 +0000 UTC; Views: 10741; Favourites: 63; Downloads: 3
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Description
Arctodus SimusBears are among the most recognizable megafauna of continents across the globe, from the giant pandas of China to the Grizzly Bears of America, colonizing niches from herbivorous bamboo eaters to salmon and berry munchers.
However, some 13,000 years ago, a giant bear dominated North America. This was the awe-inspiring giant short-faced bear: Arctodus simus.
History and Discovery:
In 1854, one of the preeminent American paleontologists, Joseph Leidy, described a partial jaw and vertebrae from the Ashley Fossil Bed. He recognized it as a species of bear but noted it was distinct from North America's modern black and brown bears. He named the new bear genus Arctodus pristinus. The generic name is derived from the Greek word with the prefix “Arcto” as “bear” and the suffix “dus” as “tooth”. The specific name, Latinized, means “first”.
However, the species in this profile, Arctodus simus, was described by one of Leidy’s pupils, Edward Drinker Cope, in 1879. At first, he referred to it as Arctotherium simus—the South and Central American tremarctine from the Pleistocene. The term “short” in Latin regarding the holotype (a partial skeleton featuring a nearly complete skull) refers to the supposed shortened skull.
It would not be Björn Kurtén of Finland who reanalyzed the material of Arctodus and Arctotherium in 1967 and found that A.simus had more commonalities with Arctodus. Thus, it was redubbed as Arctodus simus.
Taxonomy:
Arctodus is a member of the tremarctine family—the “short-faced bears” a somewhat inaccurate moniker as will be discussed later. Today, only one member survives: Tremarctos, the spectacled bear of South America.
The family’s earliest known member, Plionarctos, evolved in the mid-to-late Miocene some 10,000,000 years ago. They likely diverged from other ursines some 15-13,000,000 years ago and became endemic to North America. By the end of the Pliocene, three members arose: Arctodus, Arctotherium, and Tremarctos itself.
As for Arctodus itself, according to most studies, it’s believed they diverged from Arctotherium and Tremarctos some 4.2-5,500,000 years ago. By the Pleistocene, Arctodus would dominate North and Central America. However, Tremarctos and Arctotherium would dwell in parts of North and Central, and eventually, both Arctotherium and Tremarctos would migrate to America.
As the name implies, A.pristinus was the first member of the genus and likely the progenitor of A.simus. Regarding where they lie taxonomically, it’s believed these are among the most basal forms in the Pleistocene, whereas Tremarctos is the most derived in Tremarctinae.
These animals arose about 3,500,000 years ago; this species in particular, Arctodus simus, lasted until the end of the Pleistocene some 12,000 years ago.
Description:
Arctodus simus is among the largest bears and one of the largest terrestrial carnivorans, beaten by its close cousin, Arctotherium angustidens.
However, Arctodus simus was the largest in North America. Like most bears, they were massively sexually dimorphic. On average, males would weigh some 1700-1800lbs whereas females could average 1000-1100lbs, massive for even the largest bears of today be it the Polar or Kodiak Bears. Males would be around 5-6ft tall at the shoulder and about 10-11ft tall when reared up. Females are about 4.5-5ft tall at the shoulder and 7-8ft tall when reared up. However, massive males found in California, Colorado, Mexico, and Alaska could’ve gotten up to 6.25-6.5ft tall at the shoulder and gotten 12-13ft tall when reared up and weighed up to 2000-2200lbs.
Contrary to popular belief, Arctodus did not have proportionally longer legs than other bears; this illusion was created by the more compact body and arched back. However, it should be noted that the limbs were indeed more gracile, allowing it to attain faster speeds and likely gallop or trot more efficiently.
Moreover, despite its moniker, the animal was not “short-faced.” While the muzzle is somewhat shortened, the skull is deeper, giving the bear its distinctive appearance, and it nor any members of its family were mainly “short-faced.”
A Dietary Question:
From the time Arctodus was first discovered in the 1980s and '90s, paleontologists thought that the Short-Faced Bear was a brutish superpredator that overwhelmed its prey with speed and bulk and fed exclusively on meat.
For a long time, this made sense. Its teeth were more robust and had reinforced tooth enamel built to tackle more rigid flesh, and its more efficient limbs would’ve enhanced it. Furthermore, early analysis of bone chemistry from a specimen in Alaska supported that idea with extremely high amounts of carbon and nitrogen in the samples.
The idea of a giant bear tackling fully grown bison, horses, or even juvenile mammoths or mastodons is an intoxicating vision for many children and paleoartists alike. Also, it’s not that farfetched, as grizzly bears have been documented killing cattle in Montana and feral horses in the northern plains. However, as cool as this image of a hypercarnivorous Arctodus is, it’s likely not the case.
In the late 90s to 2000s, other authors posited since its limbs were so gracile, it would likely not have been able to pursue prey with much agility, as a sharp turn from a horse or bison could injure the bear. This has led researchers like Paul Matheus to posit it used its size to its advantage as a specialist scavenging kleptoparasite. It’d arrive at a fresh kill of another predator, be it a dire wolf, saber-toothed cat, or American Lion, rear up and intimidate it away. Also, its deep snout was anchored by powerful jaw muscles capable of shearing through flesh and bone to get at the marrow.
Others still have used the vegetarian hypothesis in that Arctodus was a massive version of Tremarctos and ate mainly plants as re-analyzing bone chemistry shows evidence of vegetation being consumed across various localities in North America. With very flexible forelimbs, bringing vegetation to its maw would be easier. It could be explained by its massive size as its distant cousin, the cave bear Ursus spelaeus, rivaled some of the largest Arctodus during the glacial maximums of the ice age.
However, the most accepted theory is the short-faced bear had a similar diet to modern grizzlies. And by that… it’d have varied from population to population, but primarily an omnivore. Some would’ve been more omnivorous, others more carnivorous, as will be discussed in the following section.
Habitat and Variety of its Diets:
Arctodus simus ranged from as far south as southern Mexico and as far north as Alaska. As far west as California and as far east as Pennsylvania. It was a wide-ranging animal that dwelled in many habitats.
In the regions of the Yukon, Alaska, and parts of Beringia (a land bridge between the old and new world) on the once great Mammoth Steppe, the moniker of it being a predator or scavenger holds the most weight. Arctodus simus of this region dwelled among megafauna like steppe bison, horses, saiga antelope, reindeer, muskox, and, of course, the Woolly Mammoth. In competition would’ve been megafaunal wolves, scimitar-toothed cats, and cave lions. Given the vast expanse of steppe and tundra, very few plants would be present. Thus, it’d have to rely on the only food source available: meat. They were probably ambush predators on horses, reindeer, or muskox. Also, occasionally being a scavenger on mammoth and bison carcasses.
As one moves south, the diet of these animals becomes more varied. In California, in the famous Rancho La Brea Tarpits, skulls, and teeth attributable to Arctodus show cavities formed on some molars, suggesting an intake of carbohydrates and the only one available: sugar. Sugar from both fruit and honey came across. Likely, it would’ve supplemented its diet with meat when it could, as shown that most died caught in the tarpits while trying to get to food. In this region, camels like Camelops, ancient and giant bison, horses, ground sloths, elk, tapir, deer, and American Mastodon and Columbian mammoth lived around the woodland of eastern California. In competition, the larger American Lion, saber-toothed cat (Smilodon), grizzly and black bear, and dire wolf would’ve lived in the region.
As one moves East, onto the scattered woodland of inland California and the plains and into the foothills of the Rockies. Ancient and Giant Bison roamed on the woodland and the grassland. Pronghorn frolicked on the plains, grazing on the vegetation. It’s in these regions where the diet was more or less 50/50 for Arctodus; they’d have consumed primarily mastodons, tapir, and deer in the woodland, along with some vegetation as well. Predators were the same, but animals like cougars thrived here as well.
As one moves further East and south, the population of Arctodus becomes rarer. Ground sloths like Megalonyx and Nothrotheriops were more and more prevalent. Bootherium and Euceratherium were relatives of the muskox in the central and southern parts of the US. Moose, elk, and giant Cervalces, the stag moose, were common in the eastern USA. Mastodons were found across the region, but mammoths were one of two species. The Columbian Mammoth is found in areas like Tennessee, North Carolina, and Colorado. In the North, the iconic Woolly Mammoth ruled in Montana, Oregon, Washington, and Illinois. In Virginia and Pennsylvania, Mammoth and Ground Sloth bones have tooth marks from dire wolves and Arctodus showing active competition between Arctodus and other predators of the Pleistocene.
As one moves south, the environment becomes more arid and savannah-esque. As well as some scattered forest in the region. Animals like Hemiauchenia, a camelid, and some residents of the great American Interchange, like the notoungulate Mixotoxodon and the giant ground sloths like the massive Eremotherium and the grazing Paramylodon, were around too. Armored southern immigrants like armadillos and their big cousins like Holmesina and Glyptotherium were also present, grazing on the grasses in the scrub. Proboscideans like Columbian Mammoths, American Mastodon, and the gomphothere Cuvieronius dwelled on the scattered grassland and scrubland forests of the south. Smilodon, dire wolves, and American Lions, along with some Jaguars populations, were also found here. Most interesting were the two now-extinct ursids, the Mexican Grizzly and the relative of Arctodus, and the modern spectacled bear, Tremarctos floridanus. As the specific name implies, it was discovered in Florida, but they also lived across the southern US and into Mexico. Studies from the region show niche partitioning between the bears, Tremarctos floridanus being more herbivorous, Mexican grizzlies and black bears being more omnivorous, and Arctodus simus being primarily a carnivore. According to most fossil finds, they likely hunted camelids, tapirs, and horses in this region and scavenged off Proboscideans.
Behavior:
Like most bears, Arctodus would’ve been solitary except for mothers and their cubs.
As previously shown, these animals’ behavior would’ve resembled modern grizzlies or brown bears except for a larger body size. Some are more carnivorous and hunting and scavenging; others are more omnivorous and herbivorous.
Whether or not this bear hibernates is contentious in the scientific literature; however, most paleontologists who study the bear have some theories based on various fossil finds.
Most Arctodus bears from America have been found in caves. In fact, of the 69 Arctodus finds in America, 26 of them were in caves.
These bears were likely hibernating before the cave collapsed. Interestingly, 70% of the animals found in caves are smaller specimens, suggesting female, and the other 30% are male.
Whether or not mother Arctodus simus live in caves and during hibernation and have maternal torpor where they give birth while hibernating is up for debate. However, given its cousin Arctotherium angustidens had two skeletons with a female and a baby, it’s not farfetched to suggest A.simus would’ve done the same. As will be discussed, the caves they dwelled in could have had implications for their extinction.
Extinction:
As with most species at the end of the Pleistocene, these magnificent bears died out at the dawn of the Holocene. The cause of the end-Pleistocene extinction is debated, some positing humans, others climate change, competition of brown bears, or all of the above.
In Lubbock, Texas an Arctodus fossil find shows evidence of human butchering. Marks on the ribs and limbs show scraping barks caused by stone tools. In various pre-Columbian human sites where stone tools are found, Arctodus is located nearby, too, from Ohio, Texas, and Utah. Probably most interesting was a foot bone from Spalding, Idaho, where the bone is charred; however, whether or not it was due to humans is up for debate.
Brown bears outcompeting them is an interesting suggestion, but since these animals have co-existed for thousands of years since brown bears came to America, it’s unlikely to be the case.
Climate change is also posited as the reason for its extinction and is also believed to be the most accepted component. With open to semi-open woodland fading from the US environment, more forested environments are becoming prevalent. While Arctodus did live in some woodland, the prey it lived off of couldn’t, and the changing habitat led to lower and lower quality vegetation to forage.
As for why brown bears of various subspecies persisted in the US, it is believed to be due to them being both hardier and able to hibernate in dens as compared to caves, which humans could’ve used. Furthermore, populations feeding off fish could more effectively sustain populations.
The most recently dated bone from Arctodus simus is around 12,600-11,800 years ago among the last of the magnificent tremarctines that thrived in North America. However, today, the tremarctines do still cling on in South America. The spectacled bear forages from plants in the forests and highlands in South America. Hopefully, with conservation efforts, we can prevent these magnificent animals from meeting the same fate as the giant short-faced bear.
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Ahhh… ending the year with an interesting redux of an old profile from my favorite megafaunal carnivore from the US.
I was first introduced to this bear during Land of Lost Monsters (Animal Planet version of Monsters We Met) when I was a kid. Pretty sure everyone here has seen the scene. The Clovis hunter returns to the slain Woolly Mammoth kill and the short-faced bear killed him because the guy was a dumbass who ran away from the hyper carnivorous apex predator.
Honestly, that was one of the most memorable depictions of Arctodus I had ever seen.
I decided to depict a scene of an Arctodus simus scavenging a Californian Tapir. Also, because it’s nearly the end of the year, I just came home from a plane ride, wrote this on my phone, and just spell-checked it.
Will this be in Past Meets Present? Yes, it will. I’ve got scenes planned out and as for where it’ll be? What population will it be in? Think its obvious.
Happy New Year and look forward to finishing out PMP!
By Lgcfm and Ulquiorra:
Giant Short-faced Bear (Lgcfm & Ulquiorra) | ZT2 Download Library Wiki | Fandom
Tapir by DemonHunterZT2 :
California Tapir (Demon Hunter) | ZT2 Download Library Wiki | Fandom
For Past Meets Present:
Past Meets Present - Page 5 - The ZT2 Round Table
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